Simplify the following expression: $t = \dfrac{10}{9k} - \dfrac{1}{8k}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $9k$ and $8k$ $\lcm(9k, 8k) = 72k$ $ t = \dfrac{8}{8} \cdot \dfrac{10}{9k} - \dfrac{9}{9} \cdot \dfrac{1}{8k} $ $t = \dfrac{80}{72k} - \dfrac{9}{72k}$ $t = \dfrac{80 -9}{72k}$ $t = \dfrac{71}{72k}$